You can check: http://en.wikipedia.org/wiki/PageRank But it is a simplified algorithm. Original pr formula has 500 milions of variables...impossible to guess. Most important is quality/quantity of pr backlinks.. Thanks
It is simple that PR is always calculated on behalf of the inbound links pointing to your website. I think you can get your desired knowledge from here and it would be helpful to you - pr.efactory.de/e-pagerank-algorithm.shtml sirgroane.net/google-page-rank/ And wiki as well. your most confusing points would be cleared here after reading the stuff.